Techniques are provided to determine a more realistic measure of a physical carrier-to-interference plus noise radio (pCINR) associated with a wireless channel between first and second wireless communication devices. Channel conditions are used to derive a channel margin quantity that is in turn used “discount” the pCINR. The discounted pCINR is then used to determine a modulation and encoding scheme that can be used on the wireless channel for communications between the first and second wireless communication devices.